Seed magazine

ABSTRACT

The invention provides magazines for radioactive brachytherapy seeds. The seed magazines provided herein include housing, seed holder, and pusher components, and optionally have a slidable shield to protect a user from radiation.

PRIORITY CLAIM/RELATED APPLICATION

This application in a continuation of and claims priority under 35 USC120 to U.S. patent application Ser. No. 11/196,659 filed on Aug. 2, 2005and entitled “Seed Magazine” which is a continuation of and claimspriority under 35 USC 120 to U.S. patent application Ser. No. 10/354,950filed Jan. 29, 2003, now U.S. Pat. No. 6,953,426, which is incorporatedherein by reference.

TECHNICAL FIELD

This invention relates to magazines for radioactive seeds such as thoseused with brachytherapy devices.

BACKGROUND

Brachytherapy is a form of cancer treatment in which radiation sourcesare placed inside a patient's body to irradiate a tumor. Inbrachytherapy, a surgeon usually implants several radioactive seeds inor around a tumor, thus providing a radiation dose to the tumor. Carefulplacement of the radioactive seeds allows localized and preciseirradiation of the tumor. Because the radiation dose diminishes rapidlyoutside the radioactive seed, the radiation dose to surrounding healthytissues is minimized. Many forms of cancer respond to brachytherapy,including several forms of prostate cancer. Brachytherapy generally isless invasive than surgery, usually results in fewer side effects thansurgery or external beam radiation, allows for a short recovery time,and reduces the impact on the patient's quality of life.

Radioactive seeds typically are rice grain sized (generally about 0.8 mmby 4.5 mm), roughly cylindrical objects containing very small amounts ofradioactive material. In one widely practiced brachytherapy procedure,the radioactive seeds are implanted permanently inside the patient'sbody. The half-life of the radioactive material is generally short, andthe radioactivity in the seeds decays after about three to six months tothe point that there is little detectable radiation. Two radioactiveisotopes commonly used for permanent implants are iodine-125, often usedto treat slower growing tumors, and palladium-103, which is preferredwhen a tumor is fast growing. Other radioactive materials have been usedin implants as well.

SUMMARY

The invention relates to magazines for holding radioactive objects suchas brachytherapy seeds. In particular, the invention provides seedmagazines having a housing, a seed holder, and a pusher. Seed magazinesalso can have a shield (e.g., a slidable shield) that can protect a userfrom radioactivity emitted by seeds contained within the magazines.

The seed magazines provided herein typically are configured forinstallation into a brachytherapy device (e.g., a brachytherapy seedapplicator). During brachytherapy procedures, a seed applicator that isengaged with a seed magazine and attached to a needle is inserted into apatient for delivery of radioactive seeds to the patient. Blood cellscan migrate from the patient into the seed applicator, and can becomelodged in the applicator at or near magazine retaining structuresdesigned to retain the seed magazine within the applicator. For example,blood and other debris can obstruct the proper functioning of theball-plunger used to secure seed magazines into standard seedapplicators such as the Mick® 200-TP and 200-TPV seed applicators.

The seed magazines provided herein can be configured to be installed inbrachytherapy devices (e.g., Mick seed applicators) without engagingmagazine retaining structures within the applicators. Such seedmagazines therefore can be easily inserted into and removed frombrachytherapy devices. In addition, the seed magazines provided hereincan have springs or other structures to facilitate retention withinbrachytherapy devices, rather than relying on magazine retainingstructures within such devices.

The seed magazines provided herein also can have markings to indicatehow many seeds, if any, remain within the magazine. Thus, a user doesnot have to visualize the seeds to know how many seeds the magazinecontains, reducing the user's exposure to radiation from the seeds.

The invention features a seed magazine having a housing, a seed holder,and a pusher, wherein the seed holder has a surface defining a recess atleast one millimeter in length. The seed holder can have a proximal endand a distal end, and the recess can extend from the proximal end towardthe distal end. The recess can define a channel that extends to an endof the seed holder. The recess can be centrally located between twoedges of the surface. The recess can be defined by no more than twosurfaces of the seed holder. The recess can be between three and eightmillimeters in length (e.g., between five and six millimeters inlength). The maximum width of the recess can be less than fivemillimeters (e.g., between 0.5 and 2.5 millimeters).

The seed holder can have two adjacent surfaces, where the first surfacedefines at least one spring and the second surface defines a space, andwhere the space is positioned such that the at least one spring can moveat least partially into the space when force is applied to the firstsurface. The seed holder can have a surface, where the surface defines aprotrusion, and where the protrusion exerts force against abrachytherapy device when the seed magazine is engaged with thebrachytherapy device.

The seed magazine can further include a shield, where the seed holderdefines a slot for retaining radioactive seeds, and where at least aportion of the shield is positioned over the seed holder. The shield canbe slidably movable within the housing and the pusher. The shield canmove slidably within the housing and the pusher to obstruct the view ofradioactive seeds within the seed magazine.

The pusher can have markings. The space between the markings can beequal to the thickness of a seed.

The housing can be hollow. The external surface of the housing candefine external threads and the internal surface of the housing candefine internal threads, and the external and internal threads can havethe same pitch. The external and internal threads can be offset tomaximize the thickness of the housing between the external and internalthreads.

The pusher can have a distal end and a disc at the distal end. The disccan define a circular shape with scalloped edges. The disc can beflexible. The thickness at the edge of the disc can be less than thethickness at a point away from the edge of the disc and closer to thecenter of the disc. The thickness from the edge to the center of thedisc can be uniform. The disc can be concave or dome-shaped.

In another aspect, the invention features a seed magazine having ahousing, a seed holder, a pusher, and a shield, where the seed holderdefines a slot for retaining radioactive seeds, and where at least aportion of the shield is positioned over the seed holder. The shield canbe slidably movable within the housing and the pusher. The shield canmove slidably within the housing and the pusher to obstruct the view ofradioactive seeds within the seed magazine.

In another aspect, the invention features a seed magazine having ahousing, a seed holder, and a pusher, where the seed holder defines aslot for retaining radioactive seeds, where the seeds are not visiblefrom outside the seed magazine, and where the pusher has markings toindicate the number of seeds within the seed magazine. The space betweenthe markings can be equal to the thickness of a seed.

In yet another aspect, the invention features a seed magazine having ahousing, a seed holder, and a pusher, where the seed holder defines aslot for retaining radioactive seeds, and where the slot has a depthbetween about 1.2 millimeters and 1.65 millimeters.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention pertains. Although methods and materialssimilar or equivalent to those described herein can be used to practicethe invention, suitable methods and materials are described below. Allpublications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the present specification, including definitions, willcontrol. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a seed magazine containing seeds.

FIG. 2 is a side view of a seed magazine containing no seeds.

FIG. 3 is a side view of the components of a disassembled seed magazine.

FIG. 4 is a side view of the housing of a seed magazine.

FIG. 5 is a side view of the seed holder of a seed magazine.

FIG. 6 is a cross-sectional view of two parallel rows of seeds in theslot of a seed holder.

FIG. 7 is a close-up view of the proximal end of the seed holder of aseed magazine.

FIG. 8 is a view of the proximal end of the seed holder of a seedmagazine, showing an alternative retention member.

FIG. 9 is a view of the proximal end of the seed holder of a seedmagazine, showing an alternative retention member.

FIG. 10 is a view of the proximal end of the seed holder of a seedmagazine, showing an alternative retention member.

FIG. 11 is a side view of the pusher of a seed magazine.

FIG. 12 is a close-up view of the distal end of the pusher of a seedmagazine.

FIG. 13 is a side view of a shield for a seed magazine.

FIG. 14 is a side view of an assembled seed magazine having a shield.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The invention provides magazines for containing radioactive objects suchas brachytherapy seeds. The seed magazines typically contain severalcomponents, including a housing, a seed holder, a pusher, and,optionally, a shield. These components can be made from any material.For example, the components can be made from a plastic material such aspolysulfone, nylon, polypropylene, or polycarbonate, or from a metalsuch as stainless steel, titanium, or aluminum. Components also can bemade from a plastic material that contains particles of a metal such astungsten, titanium, lead, or stainless steel. The metal content can befrom about 5 percent by weight to about 95 percent by weight (e.g., 6,10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or94 percent by weight). In some embodiments, the metal content of a seedmagazine component can be about 40 percent to about 70 percent by weight(e.g., 41, 45, 50, 55, 60, 65, or 69 percent by weight). Seed magazinecomponents made from such plastic and metal combinations can haveplastic-like characteristics (e.g., flexibility) while providingradiation shielding.

With reference to FIGS. 1 and 2, seed magazine 10 can have housing 15,seed holder 20, and pusher 25. Pusher 25 can have distal end 28 andgauge member 30. When seed magazine 10 contains seeds, distal end 28 andgauge member 30 of pusher 25 can protrude through distal end 32 ofhousing 15, as shown in FIG. 1. When seed magazine 10 contains no seeds,distal end 28 of pusher 25 can protrude through distal end 32 of housing15, as shown in FIG. 2. In this embodiment, gauge 30 does not protrudethrough distal end 32 of housing 15 when seed magazine 10 contains noseeds. In some embodiments, however, gauge 30 can protrude throughdistal end 32 when seed magazine 10 contains no seeds.

FIG. 3 depicts seed magazine 10 in disassembled form, showing housing15, seed holder 20, and pusher 25 separate from one another. FIG. 4shows a larger view of housing 15. A cross section of housing 15 candefine any shape. As shown in FIG. 4, for example, a cross section ofhousing 15 can define a hexagonal shape. Alternatively, a cross sectionof housing 15 can define a circular, square, rectangular, or oval shape.With reference to FIGS. 3 and 4, housing 15 can be hollow, and distalend 32 of housing 15 can define distal opening 35 through which gauge 30and/or distal end 28 of pusher 25 can protrude (e.g., when seeds arepresent in seed magazine 10). Housing 15 also can have proximal end 38,which can define proximal opening 40 of housing 15. The exterior surfaceof housing 15 near proximal end 38 can define external threads 42, whichcan be used to install seed magazine 10 in a brachytherapy device. Forexample, external threads 42 can be used to screw seed magazine 10 intoa brachytherapy device such as a sterilization carrier or a seed loadingdevice (e.g., a Mick® seed sterilizer insert or a Mick® seed loadingV-block) that can be used to implant seeds into a patient. The interiorsurface of housing 15 can define internal threads 44. External threads42 and internal threads 44 can have any pitch relative to one another.In some embodiments, external threads 42 and internal threads 44 havethe same pitch, and can be offset relative to one another such that thethickness of the threaded portion of housing 15 is maximized. Such aconfiguration can allow for maximal strength of the threaded portion ofhousing 15.

FIG. 5 is a side view of seed holder 20. With reference to FIGS. 3 and5, seed holder 20 can have distal end 50 and proximal end 52. Seedholder 20 also can define slot 55, which can extend from distal end 50toward proximal end 52, and which can be used to hold radioactivebrachytherapy seeds, for example. Seed holder 20 can have top surface57, bottom surface 60, first side surface 62, and second side surface64. Top surface 57 can define opening 66 so that slot 55 and any seedscontained therein are visible. Alternatively, seed holder 20 may lackopenings such that slot 55 is not visible through seed holder 20.

Slot 55 can have any suitable size and can be configured to contain anynumber of brachytherapy seeds. Typically, slot 55 is slightly wider thanthe length of a brachytherapy seed, is slightly deeper than the diameterof a seed, and is long enough to hold the desired number of seeds. Forexample, slot 55 can be about three to about six millimeters wide (e.g.,about 3, about 3.5, about 4, about 4.5, about 5, about 5.5, or about 6millimeters wide), about 0.1 to about two millimeters deep (e.g., about0.1, about 0.3, about 0.5, about 0.75, about 0.9, about 1, about 1.25,about 1.5, about 1.75, or about 2 millimeters deep), and can holdbetween 10 and 30 seeds (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 seeds). In anotherembodiment, slot 55 can have a depth that is about twice the diameter ofa brachytherapy seed. For example, slot 55 can be between about 1.12millimeters and about two millimeters deep (e.g., about 1.15, 1.2, 1.25,1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9,1.95, or about two millimeters deep). In such an embodiment, slot 55 cancontain two parallel rows of brachytherapy seeds, and thus can holdbetween 20 and 60 seeds (e.g., 20, 22, 24, 25, 30, 35, 40, 45, 50, 55,57, or 60 seeds). As shown in FIG. 6, the rows of seeds 67 can bestaggered in slot 55.

With further reference to FIG. 5, seed holder 20 also can define channel68, which can extend between first and second side surfaces 62 and 64and through slot 55, and which can be positioned near proximal end 52 asshown in FIG. 3. When seed magazine 10 is installed in a brachytherapydevice such as an applicator having a stylet, the stylet can be insertedthrough channel 68 in order to move individual seeds out of seed holder20 and into a needle for placement within tissue. When slot 55 containstwo parallel rows of seeds, the portion of slot 55 through which channel68 passes can be configured (e.g., sloped) such that seeds can funnelinto channel 68 one at a time.

Seed holder 20 also can have external threads 70 and ridge 72, which canbe positioned toward distal end 50. External threads 70 of seed holder20 can interact with internal threads 44 of housing 15 when seedmagazine 10 is assembled. Ridge 72 can be used as a stop so that a userknows when seed holder 20 is fully installed in housing 15 (e.g., a usercan screw housing 15 onto seed holder 20 until ridge 72 abuts proximalend 38 of housing 15). External threads 70 of seed holder 20 andinternal threads 44 of housing 15 can be configured such that a minimumnumber of rotations are necessary to fully and securely install housing15 on seed holder 20. For example, the threads can be configured suchthat three, four, five, or more than five rotations are necessary toinstall housing 15 on seed holder 20 such that ridge 72 abuts proximalend 38 of housing 15. In this configuration, the force required to stripexternal threads 70 and internal threads 44 can be less than the forcerequired to break seed magazine 10, thus reducing the risk of magazinebreakage by over-tightening of housing 15 on seed holder 20.

With further reference to FIG. 5, bottom surface 60 and proximal end 52of seed holder 20 can define recess 75. Brachytherapy devices such asthe Mick® 200-TP and 200-TPV seed applicators typically contain amagazine retaining structure such as a ball-plunger, for example. Suchstructures can become jammed or otherwise unworkable after repeated useand sterilization. Recess 75 can be configured such that seed holder 20will not interact (or will interact minimally) with a magazine retainingstructure, and any jamming of a magazine retaining structure will notaffect the insertion or removal of seed holder 20 into/from a device.Recess 75 can have any length, width, and depth. For example, recess 75can have a length between 0.5 millimeter and 8 millimeters (e.g., 0.75,1, 1.5, 2, 2.5, 3, 3.5, 4, 4.3, 4.5, 4.8, 5, 5.3, 5.5, 5.8, 6, 6.5, 7,7.5, or 7.75 millimeters). Recess 75 can have a maximum width between0.1 millimeter and 3 millimeters (e.g., 0.15, 0.2, 0.3, 0.5, 0.75, 1,1.5, 2, 2.5, or 2.75 millimeters). Recess 75 can have a depth between0.1 millimeter and 3 millimeters (e.g., 0.15, 0.2, 0.3, 0.4, 0.5, 0.75,1, 1.5, 2, 2.5, or 2.75 millimeters).

Recess 75 can define a channel that extends along bottom surface 60 toproximal end 52 of seed holder 20. The channel defined by recess 75 canhave a solid bottom surface, such that recess 75 does not extend into acavity (e.g., the slot where the seeds can be placed) of seed holder 20.A channel defined by recess 75 can have opposing walls. Typically, nomore than two surfaces of seed holder 20 (e.g., bottom surface 60 andproximal end 52) define recess 75. Recess 75 can have a width that isnarrower than the width of cut-out 77. Recess 75 also can be centrallylocated between two edges of at least one of the surfaces of seed holder20, and typically is not located at a corner of seed holder 20 wherethree surfaces can come together to form a point. Recess 75 can benon-circular in shape.

Bottom surface 60, side surface 64, and proximal end 52 of seed holder20 can define cut-out 77. Cut-out 77 can be configured to fit around aplacement pin within a brachytherapy device such as a Mick® 200-TP or200-TPV seed applicator. Thus, cut-out 77 can facilitate the properinsertion of seed magazine 10 into a brachytherapy device having aplacement pin, as seed magazine 10 can be fully inserted into such adevice only when cut-out 77 faces the placement pin. Cut-out 77 can havea width that is greater than that of recess 75. Typically, threesurfaces of seed holder 20 (e.g., bottom surface 60, side surface 64,and proximal end 52) define cut-out 77. Cut-out 77 can be configuredsuch that a channel is not formed. For example, cut-out 77 can beconfigured such that it lacks two opposing walls.

Seed holder 20 can have a retention member such as spring 78, which canbe defined by top surface 57 as shown in FIG. 5. Alternatively, bottomsurface 60, first side surface 62, or second side surface 64 can definesuch a retention spring. When top surface 57 defines spring 78, firstside surface 62 can define space 80 such that spring 78 can flex atleast partially into space 80 when seed holder 20 is inserted into abrachytherapy device. If bottom surface 60, first side surface 62, orsecond side surface 64 define a retention spring, an adjacent surfacecan define a space analogous to space 80. Space 80 can have any length,width, and depth. For example, space 80 can have a length between 0.5millimeter and 6 millimeters (e.g., 0.75, 1, 1.5, 2, 2.5, 3, 3.5, 4,4.5, 5, 5.5, or 5.75 millimeters), a width between 0.1 millimeter and 3millimeters (e.g., 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.5, 2, 2.5, or2.75 millimeters), and a depth between 0.1 millimeter and 3 millimeters(e.g., 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.5, 2, 2.5, or 2.75millimeters). Space 80 can define a bottom surface, such that it doesnot extend into a cavity (e.g., the slot where the seeds can be placed)of seed holder 20. Space 80 typically is not located at a corner of seedholder 20 where three surfaces can come together to form a point. Space80 can have a width that is narrower than that of cut-out 77.

FIG. 7 is a close-up view of proximal end 52 of seed holder 20, showingspring 78. With reference to FIG. 7, top surface 57 of seed holder 20also can define spring 82, while second side surface 64 can define space84 under spring 82 so that spring 82 can flex when seed holder 20 isinserted into a brachytherapy device. FIG. 7 also shows seeds (e.g.,seed 67) in slot 55 of seed holder 20.

FIGS. 8, 9, and 10 depict seed holders having other embodiments of aretention member. As depicted in FIG. 8, seed holder 100 can have topsurface 105, which can define recess 110. Recess 110 further can definespace 115, which can contain protrusion 120. Protrusion 120 can extendfrom seed holder 100 and, when seed holder 100 is inserted into abrachytherapy device, can exert force against the brachytherapy devicesuch that seed holder 100 is retained within the device. For example,protrusion 120 can exert force on a magazine retaining structure (e.g.,the ball of a jammed ball-plunger) within a brachytherapy device suchthat seed holder 100 is retained within the device. Protrusion 120 alsocan be flexible such that it snaps into place below a magazine retainingstructure (e.g., the ball of a jammed ball-plunger) within abrachytherapy device and thus retains seed holder 100 within the device.

With reference to FIG. 9, seed holder 150 can have top surface 155,bottom surface 160, first side surface 165, and second side surface 170.The junctions of these surfaces can define one or more (e.g., one, two,three, four, or more than four) notches, such as notches 173, 176, and179, and a fourth notch at the junction of bottom surface 160 and secondside surface 170 (not visible in FIG. 9). Notches 173, 176, and 179 canbe defined by two surfaces of seed holder 150 (e.g., bottom surface 160and second side surface 170). Alternatively, notches 173, 176, and 179can extend to an end of seed holder 150 and thus can be defined by threesurfaces. Notches 173, 176, and 179 can have widths that are narrowerthan the width of cut-out 77. Notches 173, 176, and 179 can containprotrusions 182,185, and 188, respectively. These protrusions can extendfrom seed holder 150 and, when seed holder 150 is inserted into abrachytherapy device, can exert force against the brachytherapy devicesuch that seed holder 150 is retained within the device.

As shown in FIG. 10, seed holder 200 can have top surface 205 and bottomsurface 210, which can define one or more (e.g., one, two, three, four,or more than four) notches, such as notches 215, 220, and 225, and afourth notch on bottom surface 210 (not visible in FIG. 10). Notches215, 220, and 225 can be narrower than cut-out 77. Notches 215, 220, and225 typically are defined by two surfaces of seed holder 200, are notlocated where three surfaces can come together to form a point. Notches215, 220, and 225 can form channels in seed holder 200, and typically donot extend into a cavity (e.g., a slot where seeds can be placed) ofseed holder 200. Notches 215, 220, and 225 can contain protrusions 230,232, and 234, respectively. These protrusions can extend from seedholder 200 and, when seed holder 200 is inserted into a brachytherapydevice, can exert force against the brachytherapy device such that seedholder 200 is retained within the device.

FIG. 11 is a close-up view of pusher 25. With reference to FIGS. 3 and11, pusher 25 can have paddle 250 and stem 252 in addition to distal end28 and gauge member 30. Paddle 250 can be configured to fit into slot 55of seed holder 20, and can exert force on seeds that are containedwithin seed holder 20 when seed magazine 10 is assembled, for example.Stem 252 also can be configured to fit into slot 55, such that when noseeds are present in seed holder 20, paddle 250 can contact the end ofslot 55 that is nearest proximal end 52 of seed holder 20. Pusher 25also can have spring 254 (shown compressed in FIGS. 3 and 11) and plate256. When pusher 25 is in an assembled seed magazine, spring 254 canextend between plate 256 and the distal end of the housing interior, andcan cause pusher 25 to exert force against any seeds in slot 55. Spring254 can be made from any suitable material, including a metal such asstainless steel or brass, for example. Spring 254 can be designed as astandard helical spring and can work close to its yield strength at fullcompression. Thus, spring 254 can provide a near constant force on seedswithin slot 55, regardless of how many seeds are present within slot 55.

Distal end 28 of pusher 25 can define disc 258, which can be flexibleenough to be pushed through the distal opening of a seed magazinehousing but then can return to its original shape once distal end 28extends through the opening. The diameter of disc 258 can be slightlylarger than the distal opening of the housing, such that disc 258 canretain pusher 25 in the housing once distal end 28 has been pushedthrough the opening. Disc 258 can define any shape. As shown in FIG. 11,for example, disc 258 is circular. FIG. 12 shows pusher 270 with disc275, which has a cloverleaf shape with four “petals.” Alternatively,disc 258 can have any other shape (e.g., a square or triangular shape, asunburst shape having multiple points extending from a circular center,or a circular shape with scalloped edges or “petals”). The geometry ofdisc 258 can be configured to provide different insertion and removalforces (e.g., such that less force is required to insert disc 258through the distal opening of a seed magazine housing than to removedisc 258 from the housing). For example, the thickness of disc 258 canvary such that the edge of disc 258 has a thickness that is less thanthe thickness at a point away from the edge and closer to the center ofdisc 258. Alternatively, disc 258 can be of uniform thickness and havedifferent insertion and removal forces. For example, disc 258 can beconcave or dome-shaped, such that less force is required to insert disc258 through the distal opening of a seed magazine housing than to removedisc 258 from the housing.

With further reference to FIG. 11, gauge member 30 of pusher 25 can havemarkings such as numerical marking 280 and/or gauge marking 282. Whenpusher 25 is assembled into a seed magazine containing seeds, such thatgauge member 30 and distal end 28 protrude from the housing, a user canascertain how many seeds are present in the magazine by reading themarking that is closest to the distal end of the housing. For example,if five seeds are present in a seed magazine, only the portion of gaugemember 30 from distal end 28 to marking 282 will protrude from thehousing, indicating that the magazine contains “5” seeds. Numericalmarkings and gauge markings can be imprinted on, molded into, or etchedinto gauge member 30 in any manner.

Gauge member 30 can have any shape. As shown in FIG. 11, for example, across section of gauge member 30 defines a square. Alternatively, agauge member 30 can be configured such that a cross section defines acircle, a rectangle, an oval, a triangle, or any other shape. When gaugemember 30 has four sides as in FIG. 11, adjacent sides can havenumerical and gauge markings. Thus, opposite faces of gauge member 30can have numerical markings, while the other two opposite faces can havegauge markings.

Gauge member 30 can be hollow and thus can define interior space 290.Interior space 290 can include groove 292 and can be configured to housea shield such as shield 300, shown in FIG. 13. When a seed magazine isassembled, shield 300 can extend from interior space 290 through theinterior of the housing and over the slot of the seed holder, thusshielding a user from radioactive seeds contained within the magazine.Shield 300 and interior space 290 can be configured such that shield 300can slide within interior space 290. Thus, when a user holds the seedmagazine in what is typically considered an upright position (i.e., withthe seed holder at the bottom), shield 300 can slide downward out ofinterior space 290 to cover any seeds in the seed holder. A user canturn the seed magazine over from the upright position (i.e., such thatthe seed holder is at the top) in order to allow shield 300 to slideback into interior space 290, thus enabling the user to visualize anyseeds in the slot of the seed holder. Shield 300 can have protrusions302 and 304, which can prevent shield 300 from sliding completely out ofa seed magazine. For example, when a seed magazine is in an uprightposition such that the seed holder is at the bottom, shield 300 canslide down until protrusions 302 and 304 abut the distal end of the seedholder, thus preventing shield 300 from sliding any further. When a seedmagazine is inverted such that the seed holder is at the bottom, shield300 can slide toward the distal end of the pusher until protrusions 302and 304 abut a plate (e.g., plate 256) on the pusher.

Shield 300 also can have guide structure 306, which can be configured tofit into groove 292 of interior space 290. This embodiment canfacilitate the smooth sliding movement of shield 300. FIG. 14 shows seedmagazine 10 fully assembled, having housing 15, seed holder 20, pusher25, and shield 300 partially extending over seeds in seed holder 20.

With reference to FIGS. 3, 4, 5, and 11, seed magazine 10 can beassembled by inserting shield 300 into interior space 290 of pusher 25.Pusher 25 with spring 254 in place can be inserted into housing 15 suchthat disc 257 extends through distal opening 35. Paddle 250 of pusher 25then can be inserted into slot 55 of seed holder 20. Seed holder 20 andhousing 15 can be pushed toward one another until distal end 50 of seedholder 20 abuts proximal end 38 of housing 15, at which point internalthreads 44 of housing 15 can be screwed onto external threads 70 of seedholder 20. If seeds are present in slot 55, stem 252 can be pushed intohousing 15, gauge member 30 can extend from distal end 32 of housing 15,and spring 254 of pusher 25 can be compacted against the interior distalend of housing 15, thus causing pusher 25 to exert force against theseeds. If no seeds are present within slot 55, spring 254 can causepaddle 250 to extend fully into slot 55, and gauge member 30 typicallywill not extend through distal opening 35 of housing 15.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

1. A seed magazine comprising a housing, a seed holder that comprisestwo adjacent surfaces, wherein the first of said surfaces defines atleast one spring and the second of said surfaces defines a space, andwherein said space is positioned such that said at least one spring canmove at least partially into said space when force is applied to saidfirst surface, and a pusher that comprises markings that indicate anumber of seeds present in the seed holder, wherein said seed holdercomprises a surface defining a recess at least one millimeter in length.2. The seed magazine of claim 1, wherein said seed holder comprises aproximal end and a distal end, and wherein said recess extends from saidproximal end toward said distal end.
 3. The seed magazine of claim 1,wherein no more than two surfaces of said seed holder define saidrecess.
 4. The seed magazine of claim 1, wherein said recess is betweenthree and eight millimeters in length.
 5. The seed magazine of claim 1,wherein said recess is between five and six millimeters in length. 6.The seed magazine of claim 1, wherein the maximum width of said recessis less than five millimeters.
 7. The seed magazine of claim 1, whereinthe maximum width of said recess is between 0.5 and 2.5 millimeters. 8.The seed magazine of claim 1, wherein said seed magazine furthercomprises a shield, wherein said seed holder defines a slot forretaining radioactive seeds, and wherein at least a portion of saidshield is positioned over said seed holder.
 9. The seed magazine ofclaim 1, wherein the space between said markings is equal to thethickness of a seed.
 10. The seed magazine of claim 1, wherein thepusher further comprises a gauge member with the markings.
 11. The seedmagazine of claim 10, wherein the markings further comprise numericalmarkings.
 12. The seed magazine of claim 10, wherein the markingsfurther comprise gauge markings.
 13. The seed magazine of claim 10,wherein the markings are imprinted on, molded onto or etched into thegauge member.
 14. The seed magazine of claim 1, wherein said housing ishollow, wherein the external surface of said housing defines externalthreads, wherein the internal surface of said housing defines internalthreads, and wherein said external and internal threads have the samepitch.
 15. The seed magazine of claim 14, wherein said external andinternal threads are offset to maximize the thickness of said housingbetween said external and internal threads.
 16. The seed magazine ofclaim 15, wherein said shield is slidably movable within said housingand said pusher.
 17. A seed magazine comprising a housing, a seed holderthat comprises two adjacent surfaces, wherein the first of said surfacesdefines at least one spring and the second of said surfaces defines aspace, and wherein said space is positioned such that said at least onespring can move at least partially into said space when force is appliedto said first surface, and a pusher, wherein said seed holder defines aslot for retaining radioactive seeds, wherein said seeds are not visiblefrom outside the seed magazine, and wherein said pusher comprisesmarkings to indicate the number of seeds within said seed magazine. 18.The seed magazine of claim 17, wherein the space between said markingsis equal to the thickness of a seed.